1. Field of the invention
The invention relates to a control voltage generator in a transmitter arrangement for digitally modulated signals, and, more particularly, to a transmitter arrangement, whereby the modulation is a non-constant envelope modulation and the transmitter arrangement comprises a class C output amplifier.
2. Description of the prior art
In digital radio systems that do not use constant envelope modulation, the radio transmitter usually comprises a linear class A, AB or, in some instances linearized class C amplifiers. Such modulation schemes include, e.g., schemes of the QAM-type (Quadrature Amplitude Modulation), where the modulated information exists both in the signal phase and in the signal amplitude. A modulation scheme of this kind has been proposed for use in the future North-American digital mobile radiotelephone system.
Linear amplifiers have a poor efficiency compared to a nonlinear amplifier operating in class C mode. On the other hand, linearized class C amplifiers generally have complicated designs.